This invention relates to forming or securing fiber strands in sheet form and more particularly, to forming or securing fiber strands in sheet form for use in a ballistic-resistant laminate.
Unidirectional fiber materials are used in ballistic-resistant structures, and are disclosed, e.g., in U.S. Pat. Nos. 4,916,000, 4,079,161, 4,309,487, and 4,213,812. A non-woven ballistic-resistant laminate referred to by the trademark xe2x80x9cSpectra-Shieldxe2x80x9d is manufactured by Allied-Signal, Inc. The laminate structure is used in soft body armor to protect the wearer against high-velocity bullets and fragments. xe2x80x9cSpectra-shieldxe2x80x9d was made by first forming a non-woven unidirectional tape, which was composed of unidirectional polyethylene fibers and an elastic resin material that held the fibers together. The resin penetrated the fibers, effectively impregnating the entire structure with the resin product. Two layers, or arrays, of the unidirectional tape were then laminated together (cross-plied) at right angles to form a panel. The panel was then covered on both sides with a film of polyethylene. The film prevented adjacent panels from sticking together when the panels were layered in the soft body armor. The final panel was heavier and stiffer than desired for use as a ballistic-resistant panel. The weight and stiffness was due in part to the penetration of the entire structure with the resin product.
Non-woven ballistic-resistant laminates without resins are disclosed, e.g, in U.S. Pat. Nos. 5,437,905, 5,443,882, 5,443,883, and 5,547,536. A sheet of non-woven ballistic-resistant laminate structure was constructed of high performance fibers without using resins to hold the fibers together. Instead of resin, thermoplastic film was bonded to outer surfaces of two cross-plied layers of unidirectional fibers to hold the fibers in place. The film did not penetrate into the fibers. A sufficient amount of film resided between the bonded layers to adhere the layers together to form a sheet. Bonding the two layers of unidirectional fibers cross-plied to one another was necessary to meet structural requirements of the ballistic-resistant panel, such as impact force distribution. The individual sheets were placed loosely in a fabric envelope of an armored garment to form a ballistic-resistant panel.
A ballistic-resistant laminate assembly having a plurality of laminate ballistic-resistant sheets. Each laminated ballistic-resistant sheet having a first layer with a plurality of substantially parallel fiber strands positioned immediately adjacent to each other, the fiber strands of the first layer having opposing first and second services. A first laminating film is adhered to the first surface of the fiber strands of the first layer. A second laminating film is adhered to the second surface of the fiber strands , with a first and second laminating films sandwiched in the fiber strands therebetween. The first and second laminating films retain the fiber strands in parallel orientation. Adjacent laminating ballistic-resistant sheets are positioned so one of the other laminating films from one sheet is immediately adjacent to a laminating film of the adjacent ballistic-resistant. The plurality of laminated ballistic-resistant sheets are joined together in one embodiment by stitching the ballistic-resistant sheets together forming a stack of the sheets.